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Posted by HeatPro on February 11, 2006 at 17:00:00:
In Reply to: Boiler short cycling problem posted by Alan on February 11, 2006 at 16:47:58:
A high limit is not an operating control like a thermostat. It is n the circuit to stop the boiler from getting uselessly, excessively and perhaps dangerously too hot over 210F, so setting it that high will prevent the boiler from cycling on the high limit if the rest of the system has enough radiation and pumping ability to get rid of all the heat the boiler can make.
While control papers say to set the anticipator to .2, that is a catch-all, one-size-fits-all, 'rule of tumb' ideal idea that works out sometimes but not always. The anticipator current depends upon the objects in the circuit and the length of the wiring, so the best way to set an anticipator is using an ampmeter for that purpose. You read the actual amperes at the thermostat wires and set the anticipator to that meter value. .2 amps is usually too low for most of the circuits, so setting it up .1 amps at a time will extend the cycle time. Set it up from .2, wait an hour and observe the cycling rate, if it is extending the way you want it, but not enough, repeat another .1 amps up. Eventually you will have the cycling rate that is good enough if your limit, pumping, and boiler heat input match.